41 the same type of gene is often found in diverse

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41 The same type of gene is often found in diverse organisms P53 plays a role in preventing cancer Certain genes are found in a diverse array of species Sequences of closely related species tend to be more similar to each other than to distantly related species
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42 Fig. 23.14
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43 Molecular processes underlying evolution Homologous genes – 2 genes derived from the same ancestral gene Reveals molecular details of evolutionary change 2 sequences may be similar due to the same ancestral gene but not identical due to the independent accumulation of different random mutations
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44 Fig. 23.15
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45 Orthologs occur in separate species Paralogs are homologous genes within a single species Gene duplication can lead to a gene family 2 or more paralogs within the genome of a single organism Globin genes coding for oxygen binding proteins
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New Genes in Eukaryotes Have Evolved Via Exon Shuffling Exon shuffling occurs when an exon and the flanking introns are inserted into a gene producing a new gene that encodes a protein with an additional domain Proteins can alter traits and be acted upon by natural selection May occur by more than one mechanism Double crossover Transposable elements
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Fig. 23.16
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48 Horizontal gene transfer Exchange of genetic material among different species Vertical gene transfer involves evolution from pre-existing species by accumulation of mutations, gene duplications and exon shuffling Common phenomenon Prokaryotes to eukaryotes, eukaryotes to prokaryotes, between prokaryotes and between eukaryotes Widespread among bacteria
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49 Fig. 23.17
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50 Evolution also occurs at the genomic level involving changes in chromosome structure and number Compare 3 largest chromosomes in humans and apes Similar due to close evolutionary relationship Humans have 1 large chromosome 2 while apes have it divided into 2 separate chromosomes Chromosome 3 very similar but orangutans have a large inversion May have established orangutans as a new species
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51 Fig. 23.18
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